text: Photosynthesis and respiration are performed by algae and by macrophytes. Respiration is also performed by bacteria and animals. Assuming steady state (net daily average) the change in deficit will be
  where
  *  is the respiration .
  *  is the photosynthesis .
  Note that BOD only includes respiration of microorganisms e.g. algae and bacteria and not by macrophytes and animals.
  Due to the variation of light over time, the variation of the photosynthetic oxygen can be described by a periodical function over time, where time is after sunrise and before sunset
  where
  *  is the photosynthesis at a given time .
  *  is the daily maximum of the photosynthesis .
  *  is the fraction of day with sunlight, usually  day.
  *  is the time at which sun rises .
  The range of the daily average value of primary production  is typically 0.5-10 .